"Compels" is a technically correct but gives entirely the wrong impression. CRAF is a long running program that domestic airlines can voluntarily join to provide supplementary airlift in times of need. Prior to CRAF, in situations like the Berlin Airlift, civil aircraft were actually commandeered, so CRAF was created as a more organized system. They're paid an ongoing stipend for participating and maintaining some capabilities to be ready when called up.